1. Field of the Invention
The present invention relates to an imaging apparatus and an imaging method, and more particularly, to a technique of controlling the light emission timing of a flash in an imaging apparatus performing line exposure.
2. Description of Related Art
Recently, a CMOS (Complementary Metal Oxide Semiconductor) sensor is used often as an imaging device in a digital camera and a video camera owing to the advantages resulting from its configuration of having an amplifier in each unit pixel, such as suppression of the occurrence of electrical noises when reading out photoelectrically converted signal charges and less power consumption.
In an imaging device of the CMOS, however, a pixel having outputted signal charges starts to accumulate a photoelectrically converted signal again at the time point of output. Accordingly, the accumulation period shifts according to the scan timing on the imaging plane. The reading method as above is generally referred to as line exposure or as rolling shutter. In a case where signal charges are read out by this method, when the flash is used while an image is being taken, there may occur a phenomenon in which the luminance varies between the top and the bottom of the screen as is shown in FIG. 8. Such a phenomenon occurs in a case where signal charges are read out since the start till the end of light emission of the flash, that is, while the flash is flashing.
Because an image in a ⅔ region on the upper side of FIG. 8 is made up of signal charges accumulated while the flash is emitting light, the luminance is high. By contrast, because an image in a ⅓ region on the lower side of FIG. 8 is made up of signal charges accumulated after the flash emitted light, the luminance is low.
As a technique of solving such a problem, JP-A-2001-249396 discloses a technique of controlling light emission timing of the flash according to an open and close state of a focal plane shutter and an accumulation state of signal charges for a camera used for both silver salt filming and electronic filming.